Results of this test method are used to predict displacements in rock mass caused by loads from a structure or from underground construction. It is one of several tests that should be performed.

Because the jack can apply directed loads, this test method can be performed to provide an estimate of anisotropy.

In theory, the analysis of test data is straight forward; the modulus estimate requires a record of applied hydraulic pressure versus borehole diameter change, and a knowledge of the rock'Poisson'ratio. In practice, the above procedure, using the original theoretical formula, frequently has resulted in computing a material modulus that was demonstrably too low.

For analyzing the test data it is assumed that the rock mass is linearly elastic, isotropic, and homogeneous. Within these assumptions, this test method can provide useful data for rock masses for which equivalent continuous properties can not be found or estimated.

Note 1-Notwithstanding the statements on precision and bias contained in this test method; the precision of this test method is dependent on the competence of the personnel performing it, and the suitability of the equipment and facilities used. Agencies that meet the criteria of Practice D 3740 are generally considered capable of competent and objective testing. Users of this test method are cautioned that compliance with Practice D 3740 does not in itself assure reliable testing. Reliable testing depends on many factors; Practice D 3740 provides a means of evaluating some of those factors.